In a digital electrophotographic modular printing apparatus of known type, such as for example, the NexPress 2100. printer available from Eastman Kodak Company, located in Rochester, N.Y., color toner images are formed sequentially in a plurality of color imaging modules arranged in tandem, and the toner images are successively electrostatically transferred to a receiver member adhered to a transport web moving through the modules. Commercial printing apparatus of this type typically employ intermediate transfer members in the respective color printing modules for the transfer to the receiver member of individual color separation toner images. Of course, in other electrostatographic printers, each color separation toner image may be directly transferred to a receiver member.
Digital electrostatographic printers having a three, four, or more color capability may also provide an additional toner depositing assembly for depositing a clear toner. The provision of a clear toner overcoat to a color print is desirable for providing protection of the print from fingerprints and reducing certain visual artifacts. However, a clear toner overcoat will add cost and may reduce color gamut of the print; thus, it is desirable to provide for operator/user selection to determine whether or not a clear toner overcoat will be applied to the entire print. In U.S. Pat. No. 5,234,783, issued on Aug. 10, 1993, in the name of Yee S. Ng, it is noted that in lieu of providing a uniform layer of clear toner, a layer that varies inversely according to heights of the toner stacks may be used instead as a compromise approach to establishing even toner stack heights. As is known, the respective color toners are deposited one upon the other at respective locations on the receiver member and the height of a respective color toner stack is the sum of the toner contributions of each respective color and provides the print with a more even or uniform gloss. In U.S. Pat. application Ser. No. 11/062,972, filed on Feb. 22, 2005, now U.S. Pat. No. 7,236,234, issued on Jun. 26, 2007, in the names of Yee S. Ng et al., a method is disclosed of forming a print having a multicolor image supported on a receiver member wherein a multicolor toner image is formed on the receiver member by toners of at least three different colors of toner pigments which form various combinations of color at different pixel locations on the receiver member to form the multicolor toner image thereon; forming a clear toner overcoat upon the multicolor toner image, the clear toner overcoat being deposited as an inverse mask; pre-fusing the multicolor toner image and clear toner overcoat to the receiver member to at least tack the toners forming the multicolor toner image and the clear toner overcoat; and subjecting the clear toner overcoat and the multicolor toner image to heat and pressure using a belt fuser to provide an improved color gamut and gloss to the image. The inverse masks, the pre-fusing conditions, and the belt fuser set points can be optimized based on receiver member types to maximize the color gamut.
In the current ICC workflow of a digital printing apparatus, a chosen printer profile is critical to the actual color rendition of the digital source document. The ICC profile associated with a substrate in a digital printing system is controlled by the adopted printing process as well as the physical properties of that substrate. For example, the same substrate might exhibit different physical dot gain characteristics in a toner-based printing process than that of an ink-based printing process. Furthermore, in the electrophotographic printing process, the controlling parameters of the fuser, such as fusing temperature and pressure, significantly affect the printable color gamut. Thus, a substrate-specific printer ICC profile, noted as a custom ICC profile, is needed for accurate color reproduction on each substrate. While the custom profile approach is essential for jobs demanding high color accuracy, the vast availability of all substrates creates a logistic problem of maintaining the custom profile database and can generate confusion among users as to locating the correct ICC profile for a particular substrate being used. The number of custom ICC profiles for each substrate will increase even further when different halftone screens and colorant combinations also affect the color reproduction. Moreover, any modification on the printing process and/or physical/spectral properties of adopted colorants will render all previously-created printer ICC profiles less accurate or even obsolete. However, due to the significant change in the color gamut, new color profiles will need to be built for each receiver member to be used so as to obtain the desired printed color.
It is recognized that rebuilding color profiles for each receiver member substrate used based on the process described above is a costly approach. It would therefore be desirable to provide a method and apparatus that can make use of a few universal color profiles based on receiver member characteristics that gives reasonable color accuracy for the receiver members used, with improved color gamut and gloss, without having to rebuild color profiles for all receiver members. The current practice to curtail the ever-increasing size of substrate-specific printer ICC profiles is to adopt a set of universal ICC profiles according to the physical properties of substrates, which is less accurate than the aforementioned custom profile approach. The receiver member substrates are generally characterized as coated/uncoated, glossy/matte. In assigning a universal ICC profile to one substrate depending only on the physical properties of a substrate without measuring reproduced color, this technique is unable to cope with modifications of the printing process.